Freeze-proof horizontal heat exchanger



MW 9 97 M. w, CHURCH, m 35%,373

FREEZEPROOF HRIZONTAL HEAT EXCHANGER Filed March 22, 1965 ENVENTOR m if? ln Merijn W. Chu ch, Jr:

EY/MMM ATTORNEY United States Patent O 3,318,373 FREEZE-PROOF HORIZONTAL HEAT EXCHANGER Merton W. Church, Jr., Trenton, Mich., assignor to Wyandotte Chemicals Corporation, Wyandotte, Mich., a corporation of Michigan Filed Mar. ZZ, 1965, Ser. No. 441,517 4 Claims. (Cl. 165-110) This invention relates to heat exchangers and, more particularly, to heat exchangers for heating a fluid which is initially at a temperature below the freezing point of Water.

In many industries it is often desirable 'to heat fluids which are initially at a temperature below the freezing point of Water to some higher temperature which may or may not be above the freezing point of water. The most common fluids of this type are liquefied gases such as chlorine. It is often desirable to store and transport such gases in liquid form and heating the liquefied gases is often necessary. For example, in order to operate under the most desirable conditions, chlorine is often liquefied at a temperature below 30 F. and then heated to the range of to +20 F. during tank car loading operations for shipping. For `such heating purposes it is conventional in industrial plants to use condensing steam, generally low pressure exhaust steam such as that obtained from power plants. Considerations, such as convenient locations, etc., often make it neces-sary to employ a horizontal shell and tube-type heat exchanger in many applications, wherein the liquefied gas or other fluid below the freezing point of water is passed through horizontal tubes while the steam passes through -a suitable opening into the shell. The steam condenses on the surface of the tubes whereby the liquefied gas within the tubes is heated. Under normal conditions the steam condensate collects inside the shell and is discharged from the exchanger through a .suitable outlet.

For maximum heat exchange efficiency, it is desirable to discharge the condensate through a steam trap to prevcnt loss of uncondensed steam. However, the use of a steam trap, particularly where low pressure exhaust steam -is used, results in a Ibody of condensate collecting inside the condenser which often freezes due to the fact that the fluid to be heated is at least initially below the freezing point of water. In order to avoid this, it has been suggested in Ithe prior art to provide a means for rapidly draining the condensate from the heat exchanger to prevent the condensate from freezing. This precludes the use of a steam trap with its attendant efficiency since sufficiently rapid drainage generally cannot be obtained where a steam trap is employed. Further, an operation such as that involved in heating chlorine from a temperature below F. up to +10 or +20 F. for loading a tank car requires close control of the temperature to which the liquefied gas is heated. More specifically, as the tank car gradually fills, less heat in-put is required for heating the chlorine and, accordingly, a throttling-type pressure control valve on the steam inlet is employed. Since the temperature of low pressure ste-am is generally only slightly above 212 F., such throttling often results in reducing the temperature below 212 F. In some instances substantial throttling is required and the temperature is reduced substantially below 212 F. which results in flooding of the heat exchanger. Rapid drainage systems which rely -on gravity do not prevent freeze-up under these conditions since as the .steam condenses la vacuum fis created whereby rapid flow of water out of the heat exchanger is prevented by the higher pressure of the air on the outside of the heat exchanger.

Prior art attempts to solve this problem generally involved systems wherein condensed steam is employed to "ice heat an intermediate fluid in `one heat exch-anger which intermediate fluid is then circulated through a second heat exchanger to heat the liquefied gas or other fluid which enters at a temperature below the freezing point of water. The intermediate fluid employed is one which freezes at a temperature sufficiently low to accomplish this result without freezing in the coldest exchanger. Such systems have certain inherent disadvantages, particularly with respect to maintenance problems and both initial and operating expense.

Accordingly, it is a purpose of this invention to provide a horizontal heat exchanger for heating a fluid which is initially at a tempera-ture below the freezing point of water which includes a shell and one or more tubes disposed within the shell for conducting said fluid, said fluid being heated by condensing steam in the shell on the outside of the tubes wherein the problems of condensate freezing are eliminated or substantially reduced.

This invention is ybest -described with reference to the accompanying drawing wherein:

FIGURE l is a plan view in sect-ion of a presently preferred heat exchange apparatus embodying the principles ofthis invention, and

FIGURE 2 is an elevational view in section -of the heat exchange apparatus of FIGURE l.

With reference more particularly to the drawing, it can Ibe seen that the numeral 1 indicates generally the shell of the apparatus. The shell comprises a horizontal cylinder 3 closed at both ends. More specifically, the cylinder is closed at one end by a conventional head 5 affixed to the cylinder 3 by suitable means such as Welding. The opposite end of the cylinder 3 is provided with a flange 7 and is closed by means of a circular plate or cover 9 affixed to the end of cylinder 3 by suitable means, such as bolt and nut assemblies 10, bolting the cover 9 to flange 7. A conventional gasket (not shown) is provided between cover 9 and flange 7.

A pair of interconnected tubes 11 and 13 for conducting the liquefied gas is provided which extends horizontally Within the cylinder 3. Tubes 11 and |13 may be connected by a 180 elbow 15 affixed to the ends of the tubes 11 and 13 by suitable means, such as welding, or interconnected tubes 11 and 13 may, in fact, comprise a single tube bent 180. Inlet and outlet means 17 and 19 passing through the walls of the shell -1 and, more specifically, in a preferred embodiment through cover 9 and affixed thereto by suitable means, such as welding,

are connected to tubes 11 and 13 whereby the liquefied gas may be conducted into and out of said interconnected tubes 11 and 13. The inlet and outlet means 17 and 19 in a preferred embodiment merely constitute extensions or continuations of tubes 11 and 13 which pass through the cover 9 and are provided with flanges 21 and 23 or other suitable means for connection, respectively, to the source of liquefied gas or conduit connected thereto and to a conduit, tank, tank car, etc. into or through which the heated liquefied gas is to be discharged.

While a shell and tube heat exchanger employing a single pair of tubes *11 and 13 is illustrated in the drawing, a bundle of tubes may be employed for some applications in lieu of the single pair of tubes 11 and 13 depending on the amount of heat exchange surface desired for the heating operation. Where a bundle of tubes is employed, tube sheets are generally provided at each end of the bundle with the ends of the shell extending beyond the tube sheets forming chambers or headers toprovide interconnecting means for the tubes in the manner well known to those skilled in the art. A plurality of U shape tubes may also be employed whereby only one tube sheet is needed. One or more baflles may be provided in the chamber or chambers at the ends of the tube sheets wherecover 9 through which they pass.

through the wall of the shell and, more speciiically, in a preferred embodiment through the cover 9 and is aflxed thereto by suitable means such as welding.

In accordance with this invention, the tube 25 extends along the bottom of theshell and the end 27 of tube 25 opposite the inlet end is open for discharge of the steam within the shell1. In a preferred embodi-ment end 27 is turned upward to extend from the -bottom of shell 1- toward the interior thereof as shown in FIGUREZ of the drawing whereby a water hammer effect is prevented. By passing the tube 25 along the bottom of the shell 1 and introducing thesteam into the shell through the said tube, the condensate is'heated and freezing is thus prevented. A suitable ange 31 or other connecting means is provided on the inlet end of tube 25 for connection to the source of steam. An outlet 33 .is provided on the lbottom of shell 1 near the inlet for steam tube 25. The condensate 29 is discharged through outlet 33 to a conventionalsteam trap (not shown). A flange 34 or other connecting means is provided on outlet 33 for connecting to a .steam trapyor to a conduit. A support 35 yfor tubes 11, '13 and 25 in the form of a semi-circular sheet of suitable material, V,such as steel, vis provided to support thevportions of these tubes extending within the shell 1. The inlet ends of tubes 11, 13 and 25 are supported by As can be seen from the drawing, tubes 11 and 13 rest on thertop of support 35 and an opening 37 is provided near the bottom of support 35 for the passage of tube 25. Additional openport. 35. The support 35 'is preferably axed to the Vtube 25 by suitable means such as welding.

It isrto be Aunderstood that variousv changes and modications may be made in the foregoing apparatus Without departing from the spirit of the invention and scope of the appended claims.

What is claimed is:

1. In a horizontal heat exchanger for heating a fluid with condensing steam, a shell comprising a horizontal cylinder closed at both ends, a condensate outlet disposed in the bottom of said shell, at least one fluid conducting tube disposed within said shell wherein the temperature of a liquefied gas disposed Within said tube is initially below the freezing point of water, inlet and outlet means connected to said tube passing through said shell, and a steam inlet tube passing through said shell extending along the bottom of said shell with the end opposite the inlet end open for discharge of steam within said shell above the level of condensate remaining therewithin.

2. The apparatus of claim 1 wherein a plurality of interconnected fluid conducting tu'bes for the liquefied gas are disposed within said cylinder.

3. The apparatus of'claim 1 wherein said end of said steam inlet tube opposite the inlet end is turned upwor-d to yextend from the bottom of said shell toward the interior. thereof.

4. Theapparatus of claim 3 wherein a plurality of interconnected uid conducting tubes for the liquefied gas are disposed within said cylinder.

References Cited by the Examiner UNITED STATES PATENTS y2,457,022 12/1948 Yuia 165-110 x 2,901,225 s/1959 Abrams -109 x ROBERT A. OLEARY, Primary Examiner. MEYER PERLIN, Examiner.

T. W. STREULE, Assistant Examiner. 

1. IN A HORIZONTAL HEAT EXCHANGER FOR HEATING A FLUID WITH CONDENSING STEAM, A SHELL COMPRISING A HORIZONTAL CYLINDER CLOSED AT BOTH ENDS, A CONDENSATE OUTLET DISPOSED IN THE BOTTOM OF SAID SHELL, AT LEAST ONE FLUID CONDUCTING TUBE DISPOSED WITHIN SAID SHELL WHEREIN THE TEMPERATURE OF A LIQUEFIED GAS DISPOSED WITHIN SAID TUBE IS INITIALLY BELOW THE FREEZING POINT OF WATER, INLET AND OUT- 